ERBB2 and breast cancer: In addition, it has been reported in DESTINY-Breast04 that preliminary studies with T-DXd in patients with breast cancer expressing low levels of HER2(Immunohistochemical [IHC] staining of HER2 was defined as 1+ or 2+ and negative in situ hybridization results were defined as low expression of HER2) have shown promising effects, widening the scope of application of HER2 targeted therapy (55, 56), it is worth mentioning that this study breaks the binary pattern of anti-HER2 therapy.